The present invention relates to a golf ball and, more particularly, relates to a golf ball having dimples formed on the surface thereof to improve the carry.
In designing a golf ball, it is well known that to obtain a long carry when the golf ball is hit, a high coefficient of restitution inherent in the golf ball itself and low air resistance in the flight time caused by dimples arranged on the surface of golf ball are important. Usually, many dimples are arranged on the surface of a golf ball. To reduce the air resistance, there have been proposed various methods for arranging the dimples on the surface of golf ball at a density that is as high as possible and uniformly.
Japanese Patent Application Publication No. 2006-095281 and Japanese Patent Application Publication No. 2008-12299 describe that by arranging noncircular dimples between circular dimples, the surface occupancy ratio of dimples is increased to improve the aerodynamic performance of a golf ball. Also, Japanese Patent Application Publication No. 2007-21203 describes that the wall surface of a dimple is formed by a plurality of flat surfaces to improve the carry of a ball that has been hit.
However, the shape of the bottom surface of the noncircular dimple described in Japanese Patent Application Publication No. 2006-095281 and Japanese Patent Application Publication No. 2008-12299 is curved so as to deepen toward the center of the dimple. Therefore, although the surface occupancy ratio of dimples can be increased, there is a tendency for the depth of the dimples to increase. For such a shape, since the surface occupancy ratio of dimples is high, the air resistance during flight decreases. However, the lift of the golf ball is excessive in a high-speed region after the ball has been hit, so that there is a tendency for the golf ball to be blown upward, and there is also a tendency for the lift of golf ball to not continue for long in a low-speed region in the latter half of the trajectory. Therefore, a sufficient carry cannot be obtained.